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I've read the paper on the Lunddahl LL2733 chokes where 3 different connections are suggested. One of them are called "serial connection for improved common mode rejection". The example shows a CLC setup, but is it possible to get the same "improved common" mode rejection in a choke input PSU - and if so - how do I connect it?
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It is possible. Looking at the bottom diagram on the data sheet, "remove" the capacitor that follows the rectifier to give you a choke input diagram. Connect the audio circuit ground to the - terminal of the capacitor following the choke and the high voltage supply + to the + terminal of that same capacitor.
Kevin Carter
K&K Audio
www.kandkaudio.com
Great! Thank you.
You might still consider using a small value film cap after the rectifiers. There will be a short window in every AC cycle where the rectifiers are not conducting. As the magnetic field in the choke collapses it will generate a high voltage spike. A small cap before the choke will help mitigate that issue.
"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln
Ok, Thank you. Good to know. Tried to model it with PSU Designer II, but it didn't work out. How small should it be?
Edits: 11/07/16
My guess is you'd be looking at 0.2-1.0uF. It will increase the output voltage somewhat and also increase the output impedance of the PS by a small amount. Be sure to use a cap that is rated for high ripple current. Some of my projects that are designs of Kevin's use a Gentech 1.0uF cap that he favors and the big mono-blocks with a 600V B+ use 850V rated GE 0.68uF caps. Morgan Jones 4th ed. has a graph that illustrates the change in voltage and output impedance with different cap values.
"It is better to remain silent and thought a fool, then speak and remove all doubt." A. Lincoln
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